Hi Piotr,
SCC has built-in SMS channels for: (state of 2102 release)
- Sinch Conversation API (will be available in 2102 release)
- Sinch SMS API
- SMS365
- Social365
- Twilio
ETA for 2102 release is end of Fevruary 2021.
If you wish to use some other SMS or even social media provider, then you need to build an app that speaks one of the in-build protocols towards us and something else towards provider. Example flow could be (incoming) your SMS provider -> your app -> SMS365 interface in SCC.
This answer applies also to upcoming On Premise release, aka FP17.
BR,
Jukka
//added later//
PS. forgot to mention that Roman has experience on doing an app I was refering to.